Method of treating tubular knitted fabrics

ABSTRACT

METHOD AND APPARATUS FOR PRODUCING A FLAT KNITTED FABRIC HAVING SUITABLE EDGING TO INHIBIT UNRAVELLING. THE FABRIC IS PRODUCED FROM TUBULAR KNITTED FABRIC BY SECURING A STRIP OF THERMOPLASTIC FILM LONGITUDINALLY TO THE OUTSIDE PORTION OF THE FABRIC AND THEN SLITTING THE FABRIC ALONG THAT PORTION THEREOF COVERED BY THE FILM.

Dec. 26, 1972 T. R. COBURN METHOD OF TREATING TUBULAR KNITTED FABRICS Filed June 14, 1968 m \Om mm mm mm 2 ||il|\ mm om Q, N mm 9 NM n m. w. E

United States Patent 3,707,419 METHOD OF TREATING TUBULAR KNITTED FABRICS Theodore R. Coburn, Coventry, R.I., assignor to Bevis Industries, Inc., Providence, RI. Filed June 14, 1968, Ser. No. 737,036 Int. Cl. B3211 31/20 US. Cl. 156-250 4 Claims ABSTRACT OF THE DISCLOSURE Method and apparatus for producing a flat knitted fabric having suitable edging to inhibit unravelling. The fabric is produced from tubular knitted fabric by securing a strip of thermoplastic film longitudinally to the outside portion of the fabric and then slitting the fabric along that portion thereof covered by the film.

This invention relates to the concept of converting a knitted fabric from a normally tubular condition to a sheet fabric of the type normally obtained from a weaving operation.

It is well known that a textile fabric may be obtained considerably cheaper by a knitting operation than from a conventional weaving process. This is so, even though enormous progress has been made in connection with increasing weaving speed of the looms. However, due to the peculiar nature of knitted fabric the threads of the knitted fabric may become unravelled unless somehow locked or tied in order to prevent such unravelling. While this may be relatively easily accomplished by tying the ends of the threads, it is difficult to do this when the knitted fabric is cut thereby exposing an uncontrollable number of free ends of thread.

As was stated, knitted fabrics may be produced cheaper than woven fabrics; however, this economy may be best realized when the knitted fabric is produced in tubular fashion. Unfortunately, knitted fabric in tubular condition has limited use in the condition produced. It will be appreciated that a sheet of the knitted fabric will result when it is cut longitudinally and unfolded to assume a flattened position. Such an operation will result in two longitudinal edges of free thread ends which will be subject to unravelling.

The present invention is directed to continuously preparing tubular knitted fabric so that it can be cut longitudinally without concomitant fear of exposing the two out edges to unravelling. Within the purview of the invention, it is contemplated that a knitted fabric be collapsed, that is, folded together to form what is a flattened web having longitudinal oppositely disposed fold edges. The so-collapsed knitted tubular fabric is then heated, such as by passing it substantially around a heated drum. When the fabric is cotton the drum is heated to between about 100-350 F., preferably between 200350 F. In the event the fabric is not cotton the temperature may require different temperature ranges to take into account the possibility of scorching at higher temperatures and/ or plastic flow when some of the well known synthetic yarns are employed in the production of the knitted fabrics. The degree of heat imparted to the fabric should be sufiiciently high so that the subsequent step may be accomplished.

After the heated knitted fabric leaves the heating drum, it is moved to the next stage where a strip of thermoplastic film is positioned on at least one side of the fabric, preferably between the folds. The thermoplastic film is preferably a low density polyethylene having a thickness of 1-4 mils. By employing a relatively thin film it is quickly heated to a temperature where it will have considerable flow characteristics. By moving the so laminated knitted 3,707,419 Patented Dec. 26, 1972 "ice fabric to another heating stage and including in the second heating stage means for applying pressure to at least the laminated portions of the fabric, the thermoplastic film is secured to the fabric.

In the second heating stage the thermoplastic film fills the surface interstices of the fabric over which it has been previously positioned. The heating stages, particularly the latter, and pressure applied to the lamina must not be ex cessive whereby the thermoplastic film flows to the degree that it is permitted to bleed through the first side of the collapsed fabric to the second side whereby the first and second sides become adhesively secured together thereby defeating the possibility of carrying out one of the final steps.

After the second heating step the laminated fabric is cooled by suitable means, as by a cooling drum or roll. Thereafter the fabric is separated into a relatively uncollapsed condition again and then slit longitudinally along that portion having the thermoplastic film attached there to. The now slit fabric may be unfolded to reveal a flat single layer web. The thermoplastic film along the cut longitudinal edges prevents the unravelling of the fabric. The portion carrying the thermoplastic film acts as sort of a selvage, although it has been found that the excess portion of the film may be stripped therefrom.

For a further understanding of the invention, attention is directed to the drawings which should be considered in conjunction with the detailed description thereof set forth below wherein like reference numerals refer to like parts throughout.

FIG. 1 is a schematic view of the means of carrying out the invention.

FIG. 2 is a top plan view of a portion of the schematic view.

Reading from left to right, in FIG. 1, a previously collapsed knitted fabric 11, thereby presenting two confronting layers of fabric with folded longitudinal side edges is played around a small diameter roll 12. The fabric is then passed around the major circumference of a driven heating drum 13. As was stated in the above, the drum is maintained at a temperature of -350 F.

Then the heated fabric 11 is passed over roll 14 into the nip between roll 14 and roll 15. At the same time a relatively narrow thermoplastic film 16 is unwound from a roll thereof 17 and is passed downwardly between the nip caused by rolls 18 and 15. The play out of the film 16 is at the same rate of speed as the moving fabric 11. It will be seen that both fabric 11 and thermoplastic film 16 passes between the nip between rolls 14 and 15, thereby imparting an initial positioning of the film on the fabric 11.

The now laminated fabric is carried between the nip of pressure applying rolls 19 and 20, thereafter around a portion of roll 20 to the nip therebetween and a second heating drum 21 which is maintained at approximately the same temperature as drum 13. It Will be seen that during the pass around drum 21, the film 16 is in touching relationship with the heated surface of the drum 21 to ensure appropriate heating of the laminated fabric.

The sufliciently heated fabric is then passed over idling roll 22 and around roll 23 to the nip formed therebetween and cooling drum 24. After passing around the major portion of roll 24, the fabric is guided over roll 25 towards the separator and slitting stage. Included in this stage, taking FIG. 1 in conjunction with FIG. 2, is mandrel separator 26 positioned internally of the collapsed fabric to re-open and spread apart the fabric to a relatively substantial tubular condition with the film aflixed substantially uppermost. The separator has a groove along its top portion to accept a portion of a driven rotary slitter 27 which cuts the fabric along that portion having the film lamina. A roll 28 carries the slit fabric forward while thereafter the separator guides the fabric to a fiat unfolded condition onto an endless belt carrier 29 which travels around suitable means 30 and 31. The now slit unfolded fabric 11 is then passed between the nip of roll 31 and 32 to a further utilization stage which may include stripping of the excess film 16 from the cut edges of the fabric 11.

In the foregoing the two heating drums 13 and 21 are cooling drum 24 have a diameter of 24 inches. The throughput speed will, of course, vary but the arrangement described in the above is able to move the fabric 11 at a rate of 20-200 yards per minute. While sufficient parameters of the best mode of operation of the invention have been stated, it should be appreciated that the throughput of the fabric as stated in linear measurement per period of time elapsed is a function of the fabric treated, the heat required for effective lamination of the thermoplastic film, which in turn is a function of the diameter of the heating rolls and the temperature of the rolls.

It will be apparent that many changes and modifications of the several features described herein may be made without departing from the spirit and scope of the invention. It is, therefore, apparent that the foregoing description is by way of illustration of the invention rather than limitation of the invention.

What is claimed is:

1. A continuous method of converting elongated tubular knitted fabric into open width form comprising collapsing tubular knitted fabric into substantially a flat two layer web, passing said knitted fabric web over a drum heated to a temperature of between 100350 F., then continuously applying a strip of thermoplastic film of between 1 to 4 mils in thickness to said tubular knitted fabric as said combined strip and web pass between a pair of nip rolls, passing said combined strip and web over a drum heated to between 200350 F., with the strip engaging said last mentioned drum to press secure said strip to 4 the outer surface of said flat two layer web, cooling said web having said strip thereon to laminate said strip with said web, thereafter re-spreading apart said web to a tubular condition, and then cutting said combined strip and web longitudinally.

2. The method of claim 1 wherein the fabric is moved throughout the method steps at the rate of a linear speed of between 20 to 200 yards per minute.

3. The method of claim 1 wherein the longitudinally cut web in tubular condition is then opened to a fiat condition.

4. The method of claim 3 wherein the longitudinally cut web in tubular condition is opened to a flat condition by means of a mandrel with diverging sides which is positioned within said tubularly formed web.

References Cited UNITED STATES PATENTS 1,323,212 11/1919 Bulley l56-271 2,538,520 1/1951 Holt et al. 156270 2,593,553 4/ 1952 Francis 156247 2,653,888 9/1953 Hyman 156-271 2,714,571 8/1955 Irion et al. 156-311 3,027,287 3/1962 Hammer et a1 156-88 3,297,509 l/1967 Mercer 156271 3,437,538 4/1969 Ewing 156---271 3,486,957 12/1969 Fish et al. 15627l FOREIGN PATENTS 669,424 4/ 1952 Great Britain 156-271 BENJAMIN A. BORCHELT, Primary Examiner D. A. BENT, Assistant Examiner US. Cl. X.R. 15688 

